Phenoxypyrazole composition and process for the solvent extraction of metals

ABSTRACT

Metal extractants of 2-hydroxyphenyldiazole compounds according to Formula (2): 
     
       
         
         
             
             
         
       
         
         and tautomers and salts thereof, are disclosed, wherein substituents R 5 , R 7 , R 9 , and R 10  are as defined herein.

This application is a divisional of U.S. Application No. 13,904,089,filed May 29, 2013 (pending), which is a divisional of U.S. applicationSer. No. 13/333,117, filed Dec. 21, 2011 (now U.S. Pat. No. 8,470,052),which is a divisional of U.S. application Ser. No. 12/067,719, filedJun. 21, 2008 (now U.S. Pat. No. 8,088,810), which is the U.S. NationalPhase application of International Application No. PCT/US2006/030891,filed Aug. 7, 2006 (expired), which claims benefit of priority from U.S.Provisional Patent Application No. 60/717,042 (expired), filed Sep. 14,2005, each of which is incorporated by reference herein in its entirety.

The present invention concerns solvent extractants, solvent extractioncompositions, a solvent extraction process and especially a process forthe extraction of metals, particularly copper and nickel, from aqueoussolutions, especially solutions obtained by leaching ores.

It is known to extract metals, especially copper and nickel, fromaqueous solutions containing the metal in the form of, for example, asalt, by contacting the aqueous solution with a solution of a solventextractant in a water immiscible organic solvent and then separating thesolvent phase loaded with metal, i.e. containing at least a part of themetal in the form of a complex. The metal can then be recovered bystripping with a solution of lower pH followed for example, byelectrowinning. Most commonly, the aqueous metal-containing solutionsfor extraction are the result of the acid leaching of ores. However itis known that some metals, especially copper and nickel, can be leachedfrom certain ores with ammoniacal solutions. This has the advantage thatsolutions containing especially high concentrations of copper and nickelare derived and that there is little contamination of the solution withiron.

Several types of organic solvent extractants have been proposed for usein the recovery of metals from aqueous solutions. Whilst many of theproposed reagents have been found to work well under laboratoryconditions and demonstrate affinity for the recovery of copper andnickel or other metals from solutions, there are often problemsencountered with the application of such reagents in commercial systems.One concern is the ability of the reagent to withstand high acidic orbasic conditions. There is therefore a need for reagents, which canresist degradation under these conditions, and which show enhancedmetallurgical properties.

Accordingly, there is provided a solvent extractant comprising one ormore optionally substituted 2-hydroxyphenyldiazoles or optionallysubstituted 2-hydroxyphenyltriazoles.

Preferred are 2-hydroxyphenyldiazoles or 2-hydroxyphenyltriazoles ofFormula (1)

wherein

-   -   R⁵, R⁶, R⁷ and R⁸ each independently are hydrogen, an optionally        substituted hydrocarbyl group, an electron withdrawing group, an        electron donating group, or one or more of R⁵&R⁶, R⁶&R⁷, R⁷&R⁸        are linked in such way as to form an optionally substituted        ring;    -   Y is N or CR⁹ wherein R⁹ is hydrogen, an optionally substituted        hydrocarbyl, optionally substituted hydrocarbyloxy, optionally        substituted hydrocarbyloxycarbonyl, optionally substituted        hydrocarbylcarbonyloxy group, optionally substituted mono or        dihydrocarbylaminocarbonyl group;    -   Z is N or CR¹⁹ wherein R¹⁹ is hydrogen, an optionally        substituted hydrocarbyl, optionally substituted hydrocarbyloxy,        optionally substituted hydrocarbyloxycarbonyl, optionally        substituted hydrocarbylcarbonyloxy group, optionally substituted        mono or dihydrocarbylaminocarbonyl group;        and tautomers or salts thereof, with the provision that both Y        and Z could be N provided that no more than one of Y or Z is N.

Whilst the invention is described herein with reference to a compound ofFormula (1), it is understood that the invention relates to Formula (1)in any possible tautomeric forms, and also the complexes formed betweencompounds of Formula (1) and metals, particularly copper and nickel.

Preferred hydrocarbyl groups represented by R⁵⁻¹⁰ independently includealkyl, alkenyl and aryl groups, and any combination thereof, such asaralkyl and alkaryl, for example benzyl groups.

Preferred alkyl groups represented by R⁵⁻¹⁰ include linear and branchedalkyl groups comprising up to 36 carbon atoms, particularly from 1 to 22carbon atoms and preferably from 1 to 12 carbon atoms. When the alkylgroups are branched, the groups preferably comprise up to 5 branches inthe carbon chain, and more preferably at least 1 branch in the carbonchain. In certain embodiments, the alkyl group is cyclic, preferablycomprising from 3 to 10 carbon atoms in the largest ring and optionallyfeaturing one or more bridging rings. Examples of alkyl groupsrepresented by R⁵⁻¹⁰ include methyl, ethyl, propyl, butyl, nonyl,hexylnonyl, butylnonyl, dodecyl and cyclohexyl groups and isomersthereof.

Preferred alkenyl groups represented by R⁵⁻¹⁰ include C₂₋₂₀, andpreferably C₂₋₆ alkenyl groups. One or more carbon-carbon double bondsmay be present. The alkenyl group optionally carries one or moresubstituents, particularly phenyl substituents. Examples of mostpreferred alkenyl groups include vinyl, styryl and indenyl groups.

Preferred aryl groups represented by R⁵⁻¹⁰ contain 1 ring or 2 or morefused rings. Preferably the aryl groups include aromatic andheteroaromatic groups. When the aryl group comprises fused rings, thefused rings preferably include cycloalkyl, aryl or heterocyclic rings.Examples of aryl groups include optionally substituted phenyl, naphthyl,thienyl and pyridyl groups.

Electron withdrawing groups represented by R⁵⁻¹⁰ include halogen ornitro or optionally substituted hydrocarbyloxycarbonyl, optionallysubstituted hydrocarbylcarbonyl group, optionally substituted mono ordihydrocarbylaminocarbonyl group, including substitution by halogen,nitro SOR, SO₂R, groups.

Electron donating groups which may be represented by R⁵⁻¹⁰ includehydrocarbyl, hydrocarbyloxy, optionally substitutedhydrocarbylcarbonyloxy groups. When any of R⁵⁻¹⁰ is a substitutedhydrocarbyl or heterocyclic group, the substituent(s) should be such soas not to adversely interfere with the ability of the extractant tocoordinate to metals. Optional substituents include, but are not limitedto halogen, cyano, nitro, hydroxy, amino, thiol, acyl, hydrocarbyl,perhalogenated hydrocarbyl, heterocyclyl, hydrocarbyloxy, mono ordi-hydrocarbylamino, hydrocarbylthio, esters, carbonates, amides,sulphonyl and sulphonamido groups wherein the hydrocarbyl groups are asdefined for R⁵ above. One or more substituents may be present.

When any of R⁵ & R⁶, R⁶ & R⁷, R⁷ & R⁸, R⁸&R⁹ and R⁹ & R¹⁰ are linked insuch a way that when taken together with either the carbon atom and/oratom X of the compound of formula (1) that a ring is formed, preferablythe ring be 5, 6 or 7 membered.

When any of R⁵⁻¹⁰ is an aryl group, the aryl group is preferably aphenyl optionally substituted with one or more groups selected fromC₁₋₁₂ alkyl or halo.

Phenyl groups optionally substituted with one or more groups selectedfrom C₁₋₁₂ alkyl or halo represented by any of R⁵⁻¹⁰ include those offormula:

wherein R¹¹ to R¹⁵ each independently represent H, halo, or a C₁₋₁₂alkyl group.

When any of R¹¹ to R¹⁵ are halo, preferably the halo is Cl or F.

When any of R¹¹ to R¹⁵ are a C₁₋₁₂ alkyl group, the C₁₋₁₂ alkyl groupcan be linear or branched, and preferably is methyl, ethyl or isopropyl.

Preferably only R¹³ represents a halo group or a C₁₋₁₂ alkyl group, withR¹¹, R¹² ₅ R¹⁴ and R¹⁵ representing H.

When any of R⁵⁻¹⁰ is an optionally substituted phenyl group, it is mostpreferred that R¹¹ to R¹⁵ are all hydrogen.

Highly preferred extractant compositions of the present inventioninclude 2-hydroxyphenyldiazoles of Formula (2)

wherein

-   -   R⁵ is hydrogen, an optionally substituted hydrocarbyl group or        an electron withdrawing group;    -   R⁷ is hydrogen, or an optionally substituted hydrocarbyl group;    -   R⁹ is hydrogen, an optionally substituted hydrocarbyl,        optionally substituted hydrocarbyloxy, optionally substituted        hydrocarbyloxycarbonyl, optionally substituted        hydrocarbylcarbonyloxy group, optionally substituted mono or        dihydrocarbylaminocarbonyl group;    -   R¹⁰ is hydrogen, an optionally substituted hydrocarbyl,        optionally substituted hydrocarbyloxy, optionally substituted        hydrocarbyloxycarbonyl, optionally substituted        hydrocarbylcarbonyloxy group, optionally substituted mono or        dihydrocarbylaminocarbonyl group; and tautomers or salts        thereof.

According to a further aspect of the present invention there is provideda solvent extractant composition comprising a water immiscible organicsolvent, preferably with a low aromatic hydrocarbon content, and one ormore solvent extractants of formula (1):

as described above and tautomers or salts thereof.

Preferences for the solvent extractant of formula (1) are described asherein before in connection with the first aspect the present invention.

The composition may comprise one or more different optionallysubstituted 2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles, especially where the component optionallysubstituted 2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles are isomeric. Such isomeric mixtures may havebetter solubility in organic solvents than a single optionallysubstituted 2-hydroxyphenyldiazole or optionally substituted2-hydroxyphenyltriazole or and are preferred.

The optionally substituted 2-hydroxyphenyldiazoles or optionallysubstituted 2-hydroxyphenyltriazoles are often present in an amount ofup to 60% by weight of the composition, commonly no more than 50%, andusually no more than 40% w/w. Often, the optionally substituted2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles comprises at least 1% by weight, commonly atleast 2.5% by weight and usually at least 5% by weight of composition,and preferably comprises from 7.5 to 20%, such as about 10%, by weightof the composition.

Organic solvents which may be present in the composition include anymobile organic solvent, or mixture of solvents, which is immiscible withwater and is inert under the extraction conditions to the othermaterials present. Preferably the organic solvent has a low aromatichydrocarbon content.

Preferred organic solvents are hydrocarbon solvents which includealiphatic, alicyclic and aromatic hydrocarbons and mixtures thereof aswell as chlorinated hydrocarbons such as trichloroethylene,perchloroethylene, trichloroethane and chloroform.

Highly preferred organic solvents having a low aromatics content includesolvents and solvent mixtures where the amount of aromatic hydrocarbonspresent in the organic solvent is less than 30%, usually around 23% orless, often less than 5%, and frequently less than 1%.

Examples of suitable hydrocarbon solvents include ESCAID® 110, ESCAID®115, ESCAID® 120, ESCAID® 200, and ESCAID® 300 (hydrocarbon drillingfluids commercially available from Exxon), SHELLSOL® D70 (petroleumnaphtha−C₁₁+paraffins and naphthenics) and D80 (low viscosity, colorlesssolvent with low aromatics content and mild odor) (commerciallyavailable from Shell), and CONOSOL® C-170 (synthetic isoalkane solventcommercially available from Conoco). Suitable solvents are hydrocarbonsolvents include high flash point solvents and solvents with a higharomatic content such as SOLVESSO® 150 (an aromatic solvent naphthacommercially available from Exxon).

More preferred are solvents with a low aromatic content. Certainsuitable solvents with a low aromatic content, have aromatic contents of<1% w/w, for example, hydrocarbon solvents such as ESCAID® 110(commercially available from Exxon), and ORFOM® SX-10 and ORFOM® SX-11(each a low aromatic content solvent extraction diluent commerciallyavailable from Phillips Petroleum). Especially preferred, however ongrounds of low toxicity and wide availability, are hydrocarbon solventsof relatively low aromatic content such as kerosene, for example ESCAID®100 which is a petroleum distillate with a total aromatic content of23%, or ORFOM® SX-7, (light petroleum hydrotreated commerciallyavailable from Phillips Petroleum.

In many embodiments, the composition comprises at least 30%, often atleast 45% by weight, preferably from 50 to 95% w/w of water-immisciblehydrocarbon solvent.

Advantageously, it may be preferred to make and supply the compositionin the form of a concentrate. The concentrate may then be diluted by theaddition of organic solvents as described herein above to producecompositions in the ranges as described herein above. Where theconcentrate contains a solvent, it is preferred that the same solvent isused to dilute the concentrate to the “in use” concentration range. Inmany embodiments, the concentrate composition comprises up to 30%, oftenup to 20% by weight, preferably up to 10% w/w of water-immisciblehydrocarbon solvent. Often the concentrate composition comprises greaterthan 5% w/w of water-immiscible hydrocarbon solvent. The viscosity ofthe “azoles” of the present invention means that concentrates do notdisplay appreciably higher viscosity than extractant compositions at “inuse” concentrations. In certain high strength concentrates it may benecessary to employ a higher than normal aromatic hydrocarbon content.In such cases where a high aromatic hydrocarbon containing solvent isused in the concentrate, solvent of very low aromatic hydrocarboncontent may be used to dilute the concentrate to the “in use”concentration range.

If desired, compounds or mixtures of compounds selected from the groupconsisting of alcohols, esters, ethers, polyethers, carbonates, ketones,nitriles, amides, carbamates, sulphoxides, acids of sulphur andphosphorous compounds, for example sulphonic acids, and salts of aminesand quaternary ammonium compounds may also be employed as additionalmodifiers or kinetics boosters in the composition of the invention.Particularly preferred are mixtures comprising a first compound selectedfrom the group consisting of alcohols, esters, ethers, polyethers,carbonates, ketones, nitriles, amides, carbamates, sulphoxides, acids ofsulphur and phosphorous compounds, for example sulphonic acids, andsalts of amines and quaternary ammonium compounds and a second compoundselected from the group consisting of alkanols having from 6 to 18carbon atoms, an alkyl esters having from 7 to 30 carbon atoms, andtributylphosphate.

According to a third aspect of the present invention, there is provideda process for the extraction of a metal from solution in which an acidicsolution containing a dissolved metal is contacted with a solventextraction composition comprising a water immiscible organic solvent anda solvent extractant, whereby at least a fraction of the metal isextracted into the organic solution, characterised in that the solventextraction composition comprises a water immiscible organic solvent,preferably with a low aromatic hydrocarbon content, and a solventextractant of formula (1):

as referred to above and tautomers or salts thereof.

Metals that may be extracted in the process according to the thirdaspect of the present invention include copper, cobalt, nickel,manganese and zinc, most preferably copper.

The extractant of formula (1) and the water immiscible organic solventare as herein described before.

The aqueous acidic solution from which metals are extracted by theprocess of the third aspect of the present invention often has a pH inthe range of from −1 to 7, preferably from 0 to 5, and most preferablyfrom 0.25 to 3.5. Preferably, when the metal to be extracted is copperpH values of less than 3 are chosen so that the copper is extractedessentially free of iron, cobalt or nickel. The solution can be derivedfrom the leaching of ores or may be obtained from other sources, forexample metal containing waste streams such as from copper etchingbaths.

The concentration of metal, particularly copper, in the aqueous acidicsolution will vary widely depending for example on the source of thesolution. Where the solution is derived from the leaching of ores, themetal concentration is often up to 75 g/l and most often from 1 to 40g/l. Where the solution is a waste stream, the metal concentrations canvary from 0.5 to 2 g/l for a waste water stream, to somewhat higher forthose from other waste streams, for example Printed Circuit Board wastestreams, and can be up to 150 g/l, usually from 75 to 130 g/l.

Preferred solvent extraction compositions are those where the organicsolvent solutions may contain the optionally substituted2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles in an amount approaching 100% ligand, butpreferably the optionally substituted 2-hydroxyphenyldiazoles oroptionally substituted 2-hydroxyphenyltriazoles are employed at about 10to 40% by weight. Highly preferred solvent extraction compositions arethose comprising an organic solvent with a total aromatic content ofaround 23% or less and one or more optionally substituted2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles selected from4-alkyl-2-(5-alkyl-1H-pyrazol-3-yl)-phenol andalkyl-3-(2-hydroxyphenyl)-1H-pyrazole-5-carboxylate in a total amount ofbetween 5 to 40% by weight.

The process of the third aspect of the present invention can be carriedout by contacting the solvent extractant composition with the aqueousacidic solution. Ambient or elevated temperatures, such as up to 75° C.can be employed if desired. Often a temperature in the range of from 5to 60° C., and preferably from 15 to 40° C., is employed. The aqueoussolution and the solvent extractant are usually agitated together tomaximise the interfacial areas between the two solutions. The volumeratio of solvent extractant to aqueous solution are commonly in therange of from 20:1 to 1:20, and preferably in the range of from 5:1 to1:5. In many embodiments, to reduce plant size and to maximise the useof solvent extractant, organic to aqueous volume ratios close to 1:1 aremaintained by recycle of one of the streams.

After contact with the aqueous acidic solution, the metal can berecovered from the solvent extractant by contact with an aqueous acidicstrip solution.

The aqueous strip solution employed in the process according to thethird aspect of the present invention is usually acidic, commonly havinga pH of 2 or less, and preferably a pH of 1 or less, for example, a pHin the range of from −1 to 0.5. The strip solution commonly comprises amineral acid, particularly sulphuric acid, nitric acid or hydrochloricacid. In many embodiments, acid concentrations, particularly forsulphuric acid, in the range of from 50 to 200 g/l and preferably from150 to 180 g/l are employed. When the extracted metal is copper,preferred strip solutions comprise stripped or spent electrolyte from acopper electro-winning cell, typically comprising up to 80 g/l copper,often greater than 20 g/l copper and preferably from 30 to 70 g/lcopper, and up to 220 g/l sulphuric acid, often greater than 120 g/lsulphuric acid, and preferably from 150 to 180 g/1 sulphuric acid. Ithas been found that these compounds strip at surprisingly low acidconcentrations. This means that lower concentrations of strip acid canbe used with concomitant savings in costs, or a more normalconcentration of strip acid can be used with significant improvements inthe recovery of copper. The very low residual copper on the extractantalso means that loading in the subsequent extract cycle is moreefficient. These compositions have the additional benefit of moving acidaround the circuit. The volume ratio of organic solution to aqueousstrip solution in the process of the third aspect of the presentinvention is commonly selected to be such so as to achieve transfer, perlitre of strip solution, of up to 100 g/l of metal, especially copperinto the strip solution from the organic solution. In many industrialcopper electrowinning processes transfer is often from 10 g/l to 35 g/l,and preferably from 15 to 20 g/l of copper per litre of strip solutionis transferred from the organic solution. Volume ratios of organicsolution to aqueous solution of from 1:2 to 15:1 and preferably from 1:1to 10:1, especially less than 6:1 are commonly employed.

Both the separation and stripping process can be carried out by aconventional batch extraction technique or column contactors or by acontinuous mixer settler technique. The latter technique is generallypreferred as it recycles the stripped organic phase in a continuousmanner, thus allowing the one volume of organic reagent to be repeatedlyused for metal recovery.

A preferred embodiment of the third aspect of the present inventioncomprises a process for the extraction of a metal from aqueous acidicsolution in which:

in step 1, the solvent extraction composition comprising an extractantof formula (1) is first contacted with the aqueous acidic solutioncontaining metal,

in step 2, separating the solvent extraction composition containingmetal-solvent extractant complex from the aqueous acidic solution;

in step 3, contacting the solvent extraction composition containingmetal-solvent extractant complex with an aqueous acidic strip solutionto effect the stripping of the metal from the water immiscible phase;

in step 4, separating the metal-depleted solvent extraction compositionfrom the loaded aqueous strip solution.

According to a fourth aspect of the present invention, there is provideda process for the extraction of a metal from solution in which anaqueous ammoniacal solution containing a dissolved metal is contactedwith a solvent extraction composition comprising a water immiscibleorganic solvent and a solvent extractant, whereby at least a fraction ofthe metal is extracted into the organic solution, characterised in thatthe solvent extraction composition comprises a water immiscible organicsolvent, preferably with a low aromatic hydrocarbon content, and asolvent extractant of formula (1):

as referred to above. and tautomers or salts thereof.

Metals that may be extracted in the process according to the fourthaspect of the present invention include copper, cobalt, nickel,manganese and zinc, most preferably copper and nickel.

The extractant of formula (1) and water immiscible organic solvent areas herein described before.

The aqueous ammoniacal solution from which metals are extracted by theprocess of this aspect of the present invention often has a pH in therange of from 7 to 12, preferably from 8 to 11, and most preferably from9 to 10. The solution can be derived from the leaching of ores,particularly chalcocite ores, or may be obtained from other sources, forexample precipitated metal oxide mattes or metal containing wastestreams such as from copper etching baths.

Preferred solvent extraction compositions are those where the organicsolvent solutions may contain the optionally substituted2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles in an amount approaching 100% ligand, buttypically the optionally substituted 2-hydroxyphenyldiazoles oroptionally substituted 2-hydroxyphenyltriazoles will be employed atabout 10 to 40% by weight. Highly preferred solvent extractioncompositions are those comprising an organic solvent with a totalaromatic content of around 23% or less and one or more optionallysubstituted 2-hydroxyphenyldiazoles or optionally substituted2-hydroxyphenyltriazoles from selected from4-alkyl-2-(5-alkyl-1H-pyrazol-3-yl)-phenol andalkyl-3-(2-hydroxyphenyl)-1H-pyrazole-5-carboxylate in a total amount ofbetween 5 to 40% by weight, in a total amount of between 5 to 40% byweight.

The concentration of metal, particularly copper or nickel, in theaqueous ammoniacal solution will vary widely depending for example onthe source of the solution. Where the solution is derived from theleaching of ores, the metal concentration is often up to 75 g/l and mostoften from 1 to 40 g/l. Where the solution is a waste stream, the metalconcentrations can vary from 0.5 to 2 g/l for a waste water stream, tosomewhat higher for those from other waste streams, for example PrintedCircuit Board waste streams, and can be up to 150 g/l, usually from 75to 130 g/l. Where the solution is an ammoniacal nickel stream, the metalconcentration is most often 1-20 g/1.

The process of the fourth aspect of the present invention can be carriedout by contacting the solvent extractant composition with the metalcontaining aqueous ammoniacal solution. Ambient or elevated temperaturescan be employed, often a temperature in the range of from 15 to 60° C.,and preferably from 30 to 50° C., is employed. The aqueous solution andthe solvent extractant are usually agitated together to maximise theinterfacial areas between the two solutions. The volume ratio of solventextractant to aqueous solution are commonly in the range of from 20:1 to1:20, and preferably in the range of from 5:1 to 1:5. In manyembodiments, to reduce plant size and to maximise the use of solventextractant, organic to aqueous volume ratios close to 1:1 are maintainedby recycle of one of the streams.

After contact with the aqueous ammoniacal solution, the metal can berecovered from the solvent extractant by contact with an aqueous stripsolution having a pH lower than that from which the metal is extracted.

Alternatively, after contact with the aqueous ammoniacal solution, themetal can be recovered from the solvent extractant by contact withaqueous ammoniacal strip solution, particularly aqueous ammoniacalammonium carbonate solution. The use of aqueous ammoniacal ammoniumcarbonate solution as a stripping solution is particularly suited to therecovery of metals in the form of metal carbonates, for example Nickel.

When an aqueous strip solution having a pH lower than that from whichthe metal is extracted is employed as a strip solution in the processaccording to the fourth aspect of the present invention, the aqueousstrip solution is usually acidic and is as described for the stripsolution in the process of the third aspect of the present invention.When the extracted metal is copper, preferred strip solutions comprisestripped or spent electrolyte from a copper electro-winning cell,typically comprising up to 80 g/l, often greater than 40 g/l copper andpreferably from 50 to 70 g/l copper, and up to 220 g/l sulphuric acid,often greater than 120 g/l sulphuric acid, and preferably from 150 to180 g/l sulphuric acid.

The volume ratio of organic solution to aqueous strip solution in theprocess of the fourth aspect of the present invention is commonlyselected to be such so as to achieve transfer, per litre of stripsolution, of up to 100 g/l of metal, especially of copper or nickel intothe strip solution from the organic solution. In many industrial copperelectrowinning processes transfer is often from 10 g/l to 35 g/l, andpreferably from 15 to 20 g/l of copper per litre of strip solution istransferred from the organic solution. Volume ratios of organic solutionto aqueous solution of from 1:2 to 15:1 and preferably from 1:1 to 10:1,especially less than 6:1 are commonly employed.

When ammoniacal ammonium carbonate solution is employed as a stripsolution in the process of the fourth aspect of the present invention,the ammoniacal ammonium carbonate solution may contain excess ammoniaand is preferably stronger than the ammoniacal ammonium carbonatesolution used to leach the ore. The concentration of the solution usedto recover the metal from the loaded organic phase is preferably in theranges of NH₃: 210 to 300 gl⁻¹, CO₂: 150 to 250 gl⁻¹. Preferably, thesolution strength is close to NH₃: 270 gl⁻¹, CO₂: 230 gl⁻¹.

The contact between the loaded organic phase and the ammoniacal ammoniumcarbonate solution may be carried out at any appropriate temperature andpressure. Preferably this step is conducted at atmospheric pressure andat a temperature in the range of 20° C. to 50° C.

It is preferred that the metal loaded organic phase is contacted withthe ammoniacal ammonium carbonate solution for a period of between 30seconds to 60 minutes. Most preferably the content time is for a periodof about 3 minutes.

Both the separation and stripping process can be carried out by aconventional batch extraction technique or column contactors or by acontinuous mixer settler technique. The latter technique is generallypreferred as it recycles the stripped organic phase in a continuousmanner, thus allowing the one volume of organic reagent to be repeatedlyused for metal recovery.

When the process of the invention is applied to the operation of acontinuous counter current mixer-settler apparatus, the organic/aqueousratio in the stripping cells is preferably in the range of 6:1 to 10:1.This contrasts with the preferred organic/aqueous range in theextraction cells (where comparable organic agents may be used) of 1:1 to1.2:1.

When the metal to be recovered is Nickel, it is preferred that thenickel loaded organic phase is stripped in a stripping cell at atemperature of about 40° C. An advantage of compounds of the presentinvention is that they are more stable under these conditions thancommercial oxime extractants. The metal that separates into the aqueousphase can be recovered as a metal carbonate by any conventional manner.For example, basic nickel carbonate can readily be recovered bydistillation. Nickel can also be recovered effectively from aqueousammonium carbonate solution by hydrogen reduction under pressure. Therecovery technique preferably allows for the NH₃ and CO₂ components ofthe strip liquor to be recycled to the metal loaded organic strippingstage.

A further advantage of the compounds of the present invention is thereduced transfer of ammonia across a circuit of solutions of thecompounds of the present invention in diluent compared to solutions ofthe current oxime extractants.

A preferred embodiment of this aspect of the present invention comprisesa process for the extraction of a metal from aqueous ammoniacal solutionin which:

in step 1, the solvent extraction composition comprising an extractantof formula (3) is first contacted with the aqueous ammoniacal solutioncontaining metal,

in step 2, separating the solvent extraction composition containingmetal-solvent extractant complex from the aqueous ammoniacal solution;

in step 3, contacting the solvent extraction composition containingmetal-solvent extractant complex with an aqueous strip solution of lowerpH than the ammoniacal solution to effect the stripping of the metalfrom the water immiscible phase;

in step 4, separating the metal-depleted solvent extraction compositionfrom the loaded lower pH aqueous solution.

The metal can be recovered from the aqueous strip solution byconventional methods, for example by electrowinning

A further preferred embodiment of this aspect of the present inventioncomprises a process for the extraction of a metal from aqueousammoniacal solution in which:

in step 1, the solvent extraction composition comprising an extractantof formula (3) is first contacted with the aqueous ammoniacal solutioncontaining metal,

in step 2, separating the solvent extraction composition containingmetal-solvent extractant complex from the aqueous ammoniacal solution;

in step 3, contacting the solvent extraction composition containingmetal-solvent extractant complex with an aqueous ammoniacal stripsolution, particularly aqueous an ammoniacal ammonium carbonatesolution, to effect the stripping of the metal from the water immisciblephase;

in step 4, separating the metal-depleted solvent extraction compositionfrom the loaded aqueous ammoniacal solution.

The invention is further illustrated, but not limited, by the followingexamples.

EXAMPLES Example 1 Preparation of1-(2-hydroxy-5-nonyl-phenyl)dodecane-1,3-dione

A solution of 2-Hydroxy-5-nonylacetophenone (0.3M) in toluene (50 ml) isadded drop wise to a stirred slurry of sodium hydride (0.3M) in toluene(150 ml) at 30° C. over 30 minutes. Reaction mixture is stirred at 30°C. for 1 hour before versatic acid chloride (0.3M) is added drop wiseover 1 hour. After the acid chloride addition is complete the reactionmixture is heated to 80° C. and held at this temperature for 1 hour.Cooled to ambient and potassium hydroxide flake (0.6M) added, heated to80° C. and held at this temperature for 2 hours. Cooled to ambient andreaction mass neutralised with aqueous acetic acid solution (25%).Toluene phase is washed with water (3×25 ml) then vacuum evaporated toleave brown oil.

H¹NMR (CDCl₃, 300 Hz)

δ0.5-1.8 (multiplets, alkyl 38H), δ6.4 (singlet, CH), 66.9 (doublet,aryl H), 67.1 (multiplet, aryl H), 67.5 (multiplet, aryl H), 69.8 & 10.8(2×singlets, phenol OH & enol OH)

Example 2 Preparation of 4-Nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol

1-(2-hydroxy-5-nonyl-phenyl)dodecane-1,3-dione (0.1M) dissolved inethanol (50 ml), hydrazine hydrate (0.105M) added and the reactionsolution heated to reflux. Held at reflux for 2 hours, cooled to ambientand organic phase washed with water (2×25 ml). Toluene removed by vacuumevaporation to produce a brown oil.

Mass Spec: Mol wt 412. found 411 (M-H)⁻, 413 (M-H)⁺.

H¹NMR (CDCl₃, 300 Hz)

δ0.5-1.8 (multiplets, alkyl 38H), δ6.2 (singlet, CH), δ6.9 (doublet,aryl H), δ7.5 (multiplet, 2×aryl H), δ11.9 & 15.6 (phenol OH & pyrazoleNH)

Example 3 Preparation of n-octyl-4-(2-hydroxyphenyl)-2-4-dioxobutanoate

A mixture of 2-hydroxyacetophenone (0.15M) and ethyl pelargonate (0.45M)is added carefully to a slurry of sodium hydride (0.45M) intetrahydrofuran over 90 minutes at 50-60° C., the mixture is kept undera atmosphere of nitrogen throughout the reaction.

After addition complete the reaction mass is stirred for a further twohours at 50-60° C. Cooled to 25° C. and drowned into ice/water (600 g)before acidifying with acetic acid. Product extracted into hexane (200ml). Hexane and any unreacted starting ester removed under vacuum toyield a yellow crystalline solid. Recrystallised from hexane.

Yield=18.9 g

Mass Spec: Mol wt 275. found 275 (M-H)⁻.

H¹NMR (CDCl₃, 300 Hz)

δ0.9-2.9 (alkyl chain protons, 17H), δ6.2 (singlet, CH), δ6.9-7.8(multiplets, aryl 4H), δ12.1 & 15.0 (phenol OH & enol OH)

NMR suggests keto-enol rather than the 1,3 dione.

Example 4 Preparation ofn-octyl-3-(2-hydroxyphenyl)-1H-pyrazole-5-carboxylate

n-octyl-4-(2-hydroxyphenyl)-2-4-dioxobutanoate (0.05M) dissolved inethanol (50 ml) and sodium acetate (5 g) added. Hydrazine hydrate(0.08M) added and the reaction solution heated to reflux. Held at refluxfor 1 hours, cooled to AMBIENT and drowned into water (400 ml). Productextracted into hexane (200 ml) and the organic phase separated off andwashed with water (2×50 ml). The solvent is removed by vacuumevaporation and the product recrystallised from hexane to yield acrystalline white solid.

Wt=11.7 g

Mass Spec: Mol wt 272. found 271 (M-H)⁻, 273 (M-H)⁺.

H¹NMR (CDCl₃, 300 Hz)

δ0.9-2.8 (multiplets, alkyl 17H), δ6.45 (singlet, CH), δ6.9-7.7(multiplets, aryl 4H), δ10.1 & 11.2 (phenol OH & pyrazole NH)

Copper Extraction (comparison with a commercially available reagent,5-nonyl-2 hydroxy-acetophenone-oxime)

From Acidic Copper Sulphate Solutions Extraction Isotherms at pH 2.0

An aqueous solution containing a mixture of 3.0 g/l copper (Cu²) and 3.0g/l iron (Fe³⁺) sulphates at pH 2.0, is contacted with a ligand solution(0.2M) in ORFOM® SX-7 at varying organic to aqueous ratios. Thesolutions are stirred for one hour at 25° C., to ensure equilibrium isreached. The organic and aqueous layers are separated and the coppercontent of each phase measured by atomic adsorption.

2-hydroxy-5-nonyl- 2-(5-(1-hexylnonyl)- acetophenone-oxime 1H-pyrazol-(commercial reagent) 3-yl)-phenol Organic/Aqueous Organic AqueousOrganic Aqueous Ratio (Cu g/l) (Cu g/l) (Cu g/l) (Cu g/l) 1.5:1.0 2.020.24 2.00 0.13 1.0:1.0 2.79 0.37 2.86 0.32 1.0:1.5 3.45 0.83 3.85 0.571.0:2.0 4.31 0.97 4.64 0.83 1.0:3.0 4.87 1.69 5.33 1.33 1.0:4.0 5.011.99 6.61 1.65 1.0:8.0 5.56 2.25 6.5 2.29

Strip Isotherms

An aqueous solution containing a typical acidic spent electrolyte (30g/l copper (Cu²⁺) and 150 g/l sulphuric acid) is contacted with a ligandsolution (0.2M) in ORFOM® SX-7, (which has previously been fully loadedwith copper), at varying organic to aqueous ratios. The solutions arestirred for one hour at 25° C. to ensure equilibrium is reached. Theorganic and aqueous phases are separated and the copper content of theorganic phase measured by atomic adsorption.

2-hydroxy-5-nonyl- 4-Nonyl-2-(5-nonyl- acetophenone-oxime 1H-pyrazol-(commercial reagent) 3-yl)-phenol Organic/Aqueous Organic AqueousOrganic Aqueous Ratio (Cu g/l) (Cu g/l) (Cu g/l) (Cu g/l) 1.00:2.000.413 33.04 0.019 33.89 1.33:1.00 0.508 37.49 0.027 39.13 2.50:1.500.647 43.52 0.058 46.44

The results illustrate the improved acid strip achieved with4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol compared to a commercialreagent 2-hydroxy-5-nonyl-acetophenone-oxime.

From Ammoniacal Copper Chloride Solutions

Extraction Isotherms from Basic Solution

A typical Printed Circuit Board aqueous solution containing ammoniacalcopper chloride (113 g/l Cu²⁺/90 g/l NH₃) is contacted with a ligandsolution (0.4M) in ORFOM® SX-7 at varying organic to aqueous ratios. Thesolutions are stirred for one hour at 25° C., to ensure equilibrium isreached. The organic and aqueous layers are separated and the coppercontent of each phase measured by atomic adsorption.

4-Nonyl-2-(5-nonyl- 1H-pyrazol- 3-yl)-phenol Organic/Aqueous OrganicAqueous Ratio (Cu g/l) (Cu g/l) 10:1  8.99 24 8:1 9.8 35 4:1 11.14 692:1 12.18 90 1.5:1   12.36 95 1:1 12.25 101

Strip Isotherms

An aqueous solution containing a typical acidic spent electrolyte (30g/l copper (Cu²⁺) and 150 g/l sulphuric acid) is contacted with a ligandsolution (0.4M) in ORFOM® SX-7, (which has previously been fully loadedwith copper, 12.48 g/l Cu²⁺), at varying organic to aqueous ratios. Thesolutions are stirred for one hour at 25° C. to ensure equilibrium isreached. The organic and aqueous phases are separated and the coppercontent of the organic phase measured by atomic adsorption.

4-Nonyl-2-(5-nonyl- 1H-pyrazol- 3-yl)-phenol Organic/Aqueous OrganicAqueous Ratio (Cu g/l) (Cu g/l) 1.00:2.00 0.03 36.5 1.00:1.00 0.05 47.72.00:1.00 0.25 62.6Nickel Extraction (comparison with a commercially available reagent,5-nonyl-2 hydroxy-acetophenone-oxime)Extraction Isotherms from Ammoniacal Solution

An aqueous solution containing 10 g/l Ni²⁺/40 g/l NH₃/20 gl CO₂(prepared by dissolving ammonium carbamate (35.8 g/l) in an ammoniasolution (77 g at 32% w/w) and diluting to 1 litre with water) iscontacted with a ligand solution (0.49M) in ORFOM® SX-7 at varyingorganic to aqueous ratios. The solutions are stirred for one hour at 25°C., to ensure equilibrium is reached. The organic and aqueous layers areseparated and the nickel content of each phase measured by atomicadsorption.

2-hydroxy-5-nonyl- 2-(5-nonyl-1H- acetophenone-oxime pyrazol-3-yl)-(commercial reagent) phenol Organic/Aqueous Organic Aqueous OrganicAqueous Ratio (Ni g/l) (Ni g/l) (Ni g/l) (Ni g/l) 1.5:1.0 6.85 0.06 7.020.18 1.0:1.0 10.35 0.12 9.98 0.53 1.0:1.5 13.53 0.76 12.78 1.94 1.0:4.014.99 6.40 14.49 6.52 1.0:8.0 14.35 8.28 14.94 8.22

Strip Isotherms (A) Ammoniacal Stripping

An aqueous solution containing 280 g/l NH₃/220 g/l CO₂ (prepared bydissolving ammonium carbamate (197 g) in an ammonia solution (172 ml at32% w/w) and diluting to 500 ml with water) is contacted with a ligandsolution (0.49M in ORFOM® SX-7) (which has previously been fully loadedwith nickel) at varying organic to aqueous ratios. The solutions arestirred for one hour at 25° C. to ensure equilibrium is reached. Theorganic and aqueous phases are separated and the nickel content of theorganic phase measured by atomic adsorption.

2-hydroxy-5-nonyl- 2-(5-nonyl-1H- acetophenone-oxime pyrazol-3-yl)-(commercial reagent) phenol Organic/Aqueous Organic Aqueous OrganicAqueous Ratio (Ni g/l) (Ni g/l) (Ni g/l) (Ni g/l) 4:1 5.73 43.30 2.4658.12 6:1 7.16 54.31 4.93 68.5 10:1  9.51 68.98 8.21 80.73

The results illustrate the improved ammoniacal strip achieved with4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol compared to a commercialreagent 2-hydroxy-5-nonyl-acetophenone-oxime.

(B) Nickel can Also be Recovered Under Acid Stripping Conditions

This can be demonstrated by stripping nickel loaded organic with acidicspent electrolyte at varying organic to aqueous ratios. After stirringthe solutions for one hour at 25° C. to ensure equilibrium is reached,the organic and aqueous phases are separated and the nickel content ofthe organic phase measured by atomic adsorption.

Ammonia Transfer

An aqueous solution containing 280 g/l NH₃/220 g/l CO₂ (prepared bydissolving ammonium carbamate (197 g) in an ammonia solution (172 ml at32% w/w) and diluting to 500 ml with water) is contacted with a ligandsolution (0.49M in ORFOM® SX-7), (which had previously been fully loadedwith nickel) at varying organic to aqueous ratios. The solutions arestirred for one hour at 25° C. to ensure equilibrium is reached. Theorganic phases are separated and the ammonia content of the organicphase measured by acid/base titration.

2-hydroxy-5-nonyl- acetophenone-oxime 2-(5-(1-hexylnonyl)-1H-(commercial reagent) pyrazol-3-yl)-phenol Organic/Aqueous Organic PhaseOrganic Phase Ratio (NH₃ ppm) (NH₃ ppm) 1:1 2033 35 1:4 763 24

The results illustrate the reduced ammonia transfer into the organicphase achieved with 4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol comparedto a commercial reagent 2-hydroxy-5-nonyl-acetophenone-oxime.

Reagent Stability Tests

Stability in Contact with a Typical Acidic Spent Electrolyte

A solution of each ligand (32 ml at 0.2M) in ORFOM® SX-7 is stirred at300 rpm in contact with an aqueous solution (32 ml) containing coppersulphate (30 g/l Cu²⁺) and sulphuric acid (150 g/l) at 50° C. Samplesare taken at various intervals and the maximum copper loading of eachligand solution is measured.

2-hydroxy-5-nonyl- 2-(5-nonyl- acetophenone-oxime 1H-pyrazol-3- ContactTime (commercial reagent) yl)-phenol at 50° C. Maximum Load Maximum Load(hours) (% of start ML) (% of start ML) 0 100 100 66 93.5 100 162 91.2100 306 83.4 100

The results illustrate the significant improvement in the stability of4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol when exposed to a typicalacidic spent electrolyte compared to a commercial reagent2-hydroxy-5-nonyl-acetophenone-oxime.

Stability in Contact with Typical Ammoniacal Strip Solution

A solution of each ligand (90 ml at 0.49M) in ORFOM® SX-7, previouslyfully loaded with Ni²⁺, is stirred at 600 rpm in contact with an aqueoussolution (90 ml) containing 280 g/l NH₃/220 g/l CO₂ at 40° C. Samplesare taken at various intervals and the maximum nickel loading of eachligand solution is measured.

2-hydroxy-5-nonyl- 2-(5-nonyl-1H- acetophenone-oxime pyrazol-3- ContactTime (commercial reagent) yl)-phenol at 40° C. Maximum Load Maximum Load(hours) (% of start ML) (% of start ML) 0 100 100 19 99.8 100 67 100 100140 99.7 100 308 98.9 100 476 95.6 100 692 90.6 100 1004 70.6 100 182232.5 100

The results illustrate the significant improvement in the stability of4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol exposed to a typicalammonia/carbonate strip solution when compared to a commercial reagent2-hydroxy-5-nonyl-acetophenone-oxime.

What is claimed is:
 1. A metal extractant comprising a2-hydroxyphenyldiazole compound according to Formula (2)

wherein R⁵ is selected from the group consisting of hydrogen, anoptionally substituted C₁-C₃₆ hydrocarbyl group, halogen, and nitro; R⁷is chosen from hydrogen or an optionally substituted C₁-C₃₆ hydrocarbylgroup; each of R⁹ and R¹⁰ is independently selected from the groupconsisting of hydrogen, an optionally substituted C₁-C₃₆ hydrocarbylgroup, an optionally substituted C₁-C₃₆ hydrocarbyloxy group, anoptionally substituted C₁-C₃₆ hydrocarbyloxycarbonyl group, anoptionally substituted C₁-C₃₆ hydrocarbylcarbonyloxy group, and anoptionally substituted C₁-C₃₆ mono- or dihydrocarbylaminocarbonyl group;and tautomers or salts thereof, with the proviso that: when R⁷ is H orC₁-C₅, then at least one of R⁹ or R¹⁰ is selected from the groupconsisting of an optionally substituted C₉-C₃₆ hydrocarbyl, C₁-C₃₆alkoxy, C₁-C₃₆ hydrocarbyloxycarbonyl, C₁-C₃₆ hydrocarbylcarbonyloxy,and C₁-C₃₆ mono- or dihydrocarbylaminocarbonyl.
 2. The metal extractantcompound of claim 1, wherein each optionally substituted hydrocarbylgroup is independently selected from the group consisting of alkyl,alkenyl, aryl, alkaryl and aralkyl group.
 3. The metal extractantcompound of claim 2, wherein each optionally substituted hydrocarbylgroup is independently chosen from a branched or linear alkyl group. 4.The metal extractant compound of claim 3, wherein the alkyl groupincludes up to 23 carbon atoms.
 5. The metal extractant compound ofclaim 4, wherein the alkyl group includes up to 12 carbon atoms.
 6. Themetal extractant compound of claim 3, wherein at least one of R⁵, R⁷,R⁹, and R¹⁰ is chosen from a branched alkyl group having from 1 to 5branches in the carbon chain.
 7. The metal extractant compound of claim2, wherein the alkyl group is selected from the group consisting ofmethyl, ethyl, propyl, butyl, nonyl, hexylnonyl, butylnonyl, dodecyl,pentadecyl, heptadecyl, and cyclohexyl.
 8. The metal extractant compoundaccording to claim 1, wherein R⁷ is H, and at least one of R⁹ or R¹⁰ isa C₉-C₃₆ hydrocarbyl.
 9. The metal extractant compound according toclaim 8, wherein at least one of R⁹ or R¹⁰ is a C₉-C₁₇ alkyl.
 10. Themetal extractant compound according to claim 1, wherein each of R⁵, R⁷,and R⁹ is H; and R¹⁰ is an optionally substituted C₉-C₃₆ hydrocarbyl.11. The metal extractant compound according to claim 10, wherein R¹⁰ isan optionally substituted C₉-C₁₇ hydrocarbyl.
 12. The metal extractantcompound according to claim 11, wherein R¹⁰ is chosen from a memberselected from the group consisting of hexylnonyl, pentadecyl, andheptadecyl.
 13. The metal extractant compound according to claim 1,wherein the metal extractant compound is selected from the groupconsisting of 4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol;2-{5-[4,6,6-trimethyl-1-(1,3,3-trimethylbutyl)heptyl]pyrazol-3-yl}phenol;2-(5-nonyl-1H-pyrazol-3-yl)-phenol; and2-(5-(1-hexylnonyl)-1H-pyrazol-3-yl)-phenol.
 14. A solvent extractioncomposition comprising a water-immiscible organic solvent; and a metalextractant compound as defined by claim
 1. 15. A solvent extractioncomposition according to claim 14, wherein the metal extractant compoundis present in an amount of from 1% to 60%, from 5% to 40%, or from 7.5%to 20% by weight of the total composition.
 16. A solvent extractioncomposition according to claim 15, wherein the metal extractant compoundis present at 10% by weight of the total composition.
 17. A solventextraction composition according to claim 14, wherein at least one of R⁹or R¹⁰ of the metal extractant compound is a C₉-C₃₆ hydrocarbyl.
 18. Asolvent extraction composition according to claim 17, wherein at leastone of R⁹ or R¹⁰ is a C₉-C₁₇ alkyl.
 19. A solvent extraction compositionaccording to claim 14, wherein the metal extractant compound is selectedfrom the group consisting of 4-nonyl-2-(5-nonyl-1H-pyrazol-3-yl)-phenol;2-{5-[4,6,6-trimethyl-1-(1,3,3-trimethylbutyl)heptyl]pyrazol-3-yl}phenol;2-(5-nonyl-1H-pyrazol-3-yl)-phenol; and2-(5-(1-hexylnonyl)-1H-pyrazol-3-yl)-phenol.
 20. A solvent extractioncomposition according to claim 19, wherein the metal extractant compoundis2-{5-[4,6,6-trimethyl-1-(1,3,3-trimethylbutyl)heptyl]pyrazol-3-yl}phenol.